Guardiola made the comment during an assessment of City's title rivals, appearing to suggest Spurs were a one-man team, reliant solely on the goalscoring exploits of the prolific Kane.
The former Barcelona coach later clarified that he had intended no disrespect.
Despite already scoring five Premier League goals for Spurs this season, Kane has not hit the heights he did in the early part of last season, when he netted eight by the end of October.
But Tottenham remain well in the hunt for the Premier League title, sitting just two points adrift of City after nine matches.
"They've shown me how wrong I was," conceded Guardiola.
Monday's clash between the sides will be staged at Wembley following delays in the construction of Tottenham's new stadium at White Hart Lane.
And Guardiola believes Spurs have suffered for playing away from their traditional home since the beginning of last season, recalling a 2-0 defeat at the old stadium in north London early in his City tenure.
"I think White Hart Lane was different to Wembley. I think Tottenham feel more comfortable at home," he added. "That is going to happen anywhere. We are more comfortable at the Etihad than if we should play in another stadium.
"In that game I realised that this is the Premier League. I felt ... wow.
"I remember in that period people were saying City is going to win the Premier League.
"In that game I realised [how hard it would be] when I saw how physical they were, how good they are, how high they press, how many good things they do ... and this is a team people don't think or don't consider to be a contender to win the Premier League. I settled in England in that situation."
But Guardiola is happy to classify Spurs as title contenders and knows the importance of coming away from Wembley with three points.
"When you play against contenders it's almost six points," he commented. "The three points you win and the three points your opponent doesn't win.
"I don't know what happened in the last decade of history in the Premier League but it is true that it looks like the strong teams make a lot of points. They don't drop a lot of points. That's why the games against contenders become so important.
"But nothing is going to change because at the end, Southampton at home is the same points as Tottenham."